Process of purifying wax distillates



March 1s, 1930. E. PETTY 1,750,646

PROCESS OFPURIFYING WAX DISTILLATES med Aug. 24. 1921 @fw/fm@ Ea Dif/y l Arron/va y.

Patented Mar. 1`8, 1930 UNITED STATES PATENT OFFICE p EARL PETTY, OF WINFIELD, KANSAS, ASSIGNOR T THE DE LAVAL SEPARATOR COMPANY, 0F NEW YORK, N. Y., A CORPORATION 0F NEW JERSEY PROCESS OF PURIFYING WAX DISTILLATES Application filed August 24, 1921., Serial No. 495,079.

In the refining of crude oils, it is customary to d istill od successively products of successively higher boiling points,'such as naphtha, illuminating oil, gas oil, wax distillates, leav- 5 ing as a residue a stock commonly known as cylinder oil stock. These wax distillates carry in Solution more or less wax or paraffin)A of crystalline form. lt is desirable lor necessary to separate these wax distillates into their constituents, namely: neutral oils and wan (paraffin). Myprocess relates to the treatment of these wa'X` distillatcs.

The waX distillate is usually cut into one stream, subjected to refrigeration in order to solidify the wax, and then to press filtration to effect the separation of the oil from the wax. The pressed distillate is then run into reducingr stills and cut into various neutral oils of diderent gravities, viscosities,

colors and fire tests. v

A These processes are essentially bulk proc` esses and involve the use of large plants, the handling of a large amount of stock and the expenditure of considerable time, and moreover do not edect a thorough separation of the constituents. Moreover, the final distillations to produce light, medium and heavy stock seriously impair the color.

By my process the treatment is a continuous one, involves the handling at any one time of a relatively small amount of stock, effects the separation and purification expeditiously, dispenses with the necessity of a large and i expensive plant, secures a thorough separation, and avoids serious decolorizationin the final distilling process.

An understanding of the referred mode of executingthe process may e more readily arrived at by means of a description in con- 10 nection with a diagram ofka workable apparatus, such diagram being shown in the draw- 24lt will be understood that the elements of the apparatus are all individually old and that no claim is made herein even to any new order or arrangement ofsuch old elements, it being understood lthat the process herein described is not 'dependent for its execution upon any particular apparatus.

The first step in the execution of my prochereinafter described may be assumed to be applied to any one of them. It will, of course,

be understood that the lighter the distillate,

the smaller the proportion of a light petroleum product, such as naphtha, that need be added thereto. rlihus, lf prefer to add to the light distillate about forty-five per cent of naphtha, to the medium distillateabout fifty per centof naphtha and to the heavy distillate about fifty-ve per cent of naphtha.

The thus treated distillate is then run into a continuous agitator 10 to which is continuously added sulphuric acid. From this agitator the precipitated acid sludge, containing tarry and asphaltic materials, is drawn oli' either continuously or at intervals, while the ao treated distillate overflows into another tank 11, wherein it is washed with water. The washed acid-treated distillate is then conveyed to another tank 12, wherein it is subjected to treatment with an alkali, such as caustic soda, to neutralize the acid .and is then run through a tank 13, in which it is washed with water. instead of applying the alkali treatment in the tank 12, the stock and the caustic soda solution may be forced through a pack of eXcelsior, as more fully described in a patent issued to melluly 8,. Y 1924, No. 1,500,202.

The product now comprises an emulsion of oil stock and an alkaline solution. The emulsion is broken by means of a centrifugal separator 14 and thesoap and alkaline water Jseparated from the oil stock, which is now free. of tar and asphalt. The wax, naphtha and oil are, however, still in solution and the 10o stock contains objectionable coloring matter.

I have found it decidedly advantageous to first separate the wax fromthe oil and then treat each separately to remove the coloring matter and any tarry or asphaltic material which may not have been removed in the prior acid. alkali, washing and centrifugal treatments, thereby effecting a de- `vcided economy over the reverse treatment,

first to decolorize and then to separate; although it will be understood that the latter modification is within the broader scope of my invention.

The distillate flowing from the centrifugal separator is conveyed through any suitable chiller 15 in heat exchange relation with chilled oil that has'been separated as hereinafter described and wherein its temperature is materially reduced, and thence, through a refrigerating tank or coil 16 in heat exchange relation with a refrigerating liquid, such as refrigerated brine, thereby reducing the distillate to a temperature low enough to throw substantially all the wax out of solution.

the

n tinuous outflow of the wax.

- rlhe maximum permissible temperature will then transferred to a centrifugal separator 17, wherein the oil is separated from the wax.' It has been heretofore assumed that it is impossible, in a centrifugal separator, to centrifugally separate oil and solidified or paraffin wax and at the same time eect a con'- I have found it quite practicable, if the diluted distillate is subjected to the acid, alkali and centrifugal treatments described, to refrigerate the distillate and then, by centrifugation to eect a thorough separation of the two constituents; it being understood that the precipitated wax is not a solid in the sense of being absolutely non-flowing. While satisfactory separation and separate discharge could probably not be effected in every high speed centrifugal separator, such as an ordinary cream separator, I have found that a centrifugal separator, of essentially the type set forth in the Snyder Patent No. 1,283,343, dated October 29, 1918, will function efficiently. It will be understood, however, that the process is not limited to the use of any particular centrifugal separator and that other centrifugal separators may be found to be not only operative, but satisfactory; mention f being made of a specific type of separator in order that those skilled in the art may practice the process without the necessity of experimentingwith dierent types of separators before obtaining a sufficiently satisfactory result. It is true that the disposal of the outflowing wax may present some difficulties,

without special attention to the sludge covers to carry the wax from the bowl, in that there is a tendency of the wax, which is by no means as free-flowing as the oil, to clog the discharge spouts of the receiving pans; but this difficulty, even if not remedied, does not render the separating process impracticable. However, the objection has been entirely overcome by the provision of steam jackets applied to the receiving pan or its spouts, or both, against which the waximpinges upon its discharge from the separator bowl and which serve to so far raise the temperature of the wax as to substantially increase its fluidity, facilitate its ready discharge from the spouts of the receiving pan, and avoid clogging. This part of the process, however, is per se not my invention, it being set forth in an application filed August 24, 1921, by Cyrus Howard Hapgood, Serial No. 495,134. The wax-free oil, as it flows away from the separator 17 through the double pipe chiller 15, absorbs heat from the incoming distillate, as hereinbefore described.

Each of the separated constituents-the oilfree paraflin wax and the wax-free oll--is then separately subjected to-the following decolorizing treatment. Each of said constituents is run into a mixer 18, into which is simultaneously fed from two to ten per cent of a clarifying and decolorizing agent, such as fullers earth. The thoroughly mixed product is continuously fed into a preliminary clarifier, which maybe a vacuum filter 19 of any known efficient type, or a basket centrifuge. The preliminary clarification removes the heavier color particles. The filtered and partially clarified product is then fed into a centrifugal clarifier 20, which removes the lighter particles of coloring matter. The oil or wax (whichever may be treated) is now practically free of objectionable coloring matter as well as tar and asphalt. y

Most of the naphtha is carried off with the oil and is removed therefrom by distillation. Such distillation should be carried on at as low a temperature as possible. Any distillation tends to more or less discolor the oil, and if the preceding clarification has been very .thorough (as it is likely to be if my process is carefully carried out), it may be desirable, if complete decolorization isv desired, to relilter the oil through fullers earth.

Some naphtha will be carried out with the waX, and `it is desirable to subject the wax also to distillation with optional reclarification.

From what I have said with regard to the discoloringeffect of distillation, it is obvious that the separate treatment of the livht, medium and heavy wax distillates, as above described, removes the necessity for final ldistillation to separate the mixed distillates, thereby both simplifying the process and avoiding an otherwise inevitable serious impairment of color.

My process also has the advantage of ef- 4fecting the recovery of thel wax in crystalline i jecting each distillate separately to the following treatment: diluting the stock with a i light petroleum distillate, agitating the diluted stock with acid, removing the acid sludge, agitating the stock with an alkali, subjecting the resultant emulsion to centrifugal force'and separately flowing ,off the stock and the soap yand alkaline solution, and then subjecting the diluted stock to a separating treatment and the wax-freeoil to a decolorizing treatment: the separating treatment comprising chilling the stock 'to a temperature sufficiently low to precipitate the wax and` subjecting the resultant mixture to centrifugal force and separately flowing off the wax and the lighter products; and the@ decolorizing treatment comprising intimately mixing with the wax-free oil a clarifying and decolorizing agentand subjecting the mixture to a preliminary treatment to remove the heavier part of said agent and coloring matter and toI a centrifugal clarifying treatment to remove the lighter part of said agent and coloringmatter and finally distilling off the diluent.

2. The process of -producing purified parafiin and wax-free lubricating oils of different gravities, which comprises separately distilling vfrom the crude petroleum a plurality of wax distillates of different specific gravities and subjecting each distillate separately to the following treatment: diluting the stock with a light petroleum distillate, agitating the diluted stock with acid, removing the acid sludge, agitating' the stock with an'alkali, subjecting the resultant emulsion to centrifugal force and separately flowing off the stock and the soap and alkaline solution, then chilling the diluted stock to a temperature sufficiently low to precipitate the wax, subjecting the resultant mixture to centrifugal force and separately flowing 0E the wax and the oil, and afterward subjectlowing treatment z j therewith a clarifying and decolorizing agent ing each of the last named products to the folintimately admixing and subjecting the mixtures to a preliminary treatment to remove the heavier part of said agent and coloring matter and to a centrifugal clarifying treatment to remove the lighter part ofsaid agent and coloring matter.

3. The process of producing refined wax and wax-free oil of different specific gravities from a mineral oil stock containing wax and hydrocarbons having higher and lower boiling points than the wax, which comprises distilling off from said stock a plurality of wax distillate stocks of different specific gravities, and subjecting each distillate stock .separately to a series of operations comprising dilution with a light petroleum distillate, successive agitation of the diluted stock with acid and alkali, centrifugally breaking the emulsion produced by the alkali treatment and out-flowing the diluted stock substantially free of soap, water and alkali, refrigerating the diluted stock, centrifugally separating the wax and the lighter constituents and separately flowing od the separated products, and decolorizing each product separately.,

'f. The continuous process of producing purified paraffin wax from a mineral oil stock containing wax in solution which comprises ,subjecting a flowing stream of the stock to the following operations: agitation with acid with withdrawal of acid sludge and overflow of the treated stock, agitation with alkali, subjecting the outflowing-emulsion to centrifugal force and separately owing od the stock, refrigerating the outflowing stream of stock to precipitate the wax, subjecting the flowing mixture of wax and oil to centrifugal force and separately flowing od the wax, mixing and agitating the outflowing stream of wax with a clarifying and decolorizing agent and subjecting the liowing mixture to i a preliminary purifying treatment to remove heavier coloring matter and to a centrifugal clarifying treatment to remove lighter coloring matter..

5. The process of producing wax-free oil of different specific gravities from a mineral oil stockcontaining wax and hydrocarbons having higher and lower boiling points than the `wax, which' comprises first distilling oi from said stock a plurality of wax distillates of dierent specific gravities and afterward subjecting each wax distillate separately to dilution with a light petroleum distillate and agitation with acid and alkali, with separation of the water and soap, then refrigeratingand centrifugally separating the oil and wax, and then decolorizing each wax-free oil and distilling od the diluent, thereby avoiding a final distillation of the wax-free oil to separate the mixed distillates and the resultant impairment of color.

6. The process of producing refined wax and wax-free'oil of different specific gravities from a mineral oil stock-containing wax and hydrocarbons having higher and lower boiling points than the wax, which comprises first successively distilling olf from said stock a plurality of wax distllates of different specific gravities and afterward subjecting each wax distillate separately to dilution with a light petroleum distillate and agitation with acid and alkali, with separation of the soap and Water, then refrigerating and centrifugally separating the oil and Wax, and then separately decolorizing the Wax and Wax-free oil. f

In testimony of which invention, I have hereunto set my hand, at New York, on this 19th day of August, 1921. t

EARL PETTY. 

